Fuel injection is well known in the art for injecting fuel into a combustion chamber of an engine that is subsequently mixed with air or oxygen and then combusted for powering the engine. Fuel injectors often use control valves that control the timing and duration of a fuel injection event into the combustion chamber. As can be imagined, components of fuel injectors including the control valve may experience forces from other components or from its own inertia that causes the valve member to move. For example, when the control valve contacts another component including a valve seat or an actuating component intended to move the valve into the proper position, the control valve or another operatively connected component may move or bounce. This can lead to undesirable consequences.
By way of further example, the control valve may initiate a desirable main fuel injection event and then be moved to another position in order to stop this injection event. However, because of the forces, velocity and inertia transference of and between the various components including the valve member, the control valve may be unintentionally moved from a position where the fuel injection is prohibited to one where it is allowed due to its unintentional bouncing or other movement. This may lead to secondary, tertiary, or other after-injection events that are not intended and that may lead to an undesirable operation of the engine that leads to other problems such as poor engine performance and increased emissions. Hence, methods and devices for eliminating such valve bounce have been developed and employed.
Some control valve assemblies for fuel injectors use a lift shim that is interposed between components that move relative to each other such as a valve sleeve member and a cage member. Such lift shims have recesses that communicate the fluid that is immediately around the valve body with a pressure relief pocket or the like. These recesses are located on the top and bottom surfaces of the shim that contact the valve sleeve and cage members. It has been discovered that this shim design allows an undesirable amount of valve bounce in some applications.
Therefore, it is desirable to develop a mechanism for preventing or limiting valve bounce for a fuel injector than has yet been devised for such applications.